1. Field of the Invention
The present invention relates to a thin-film magnetic head with a magnetoresistive effect (MR) element for detecting magnetic intensity in a magnetic recording medium and for outputting a read signal, and to a manufacturing method of the thin-film magnetic head.
2. Description of the Related Art
Recently, in order to satisfy the demand for higher recording density and downsizing in a hard disk drive (HDD) apparatus, higher sensitivity and resolution of a thin-film magnetic head are required. Thus, as for a thin-film magnetic head with a recording density performance of 100 Gbspi or more, a tunnel magnetoresistive effect (TMR) head with a TMR read head element having a current perpendicular to plane (CPP) structure capable of achieving higher sensitivity and resolution is coming into practical use instead of a general giant magnetoresistive effect (GMR) head with a GMR read head element having a current in plane (CIP) structure.
The head structure in which a sense current flows in a direction parallel with surfaces of laminated layers is called as the CIP structure, whereas the other head structure in which the sense current flows in a direction perpendicular to surfaces of laminated layers is called as the CPP structure. In recent years, GMR heads with the CPP structure are being developed.
Because the CPP structure utilizes magnetic shield layers themselves as electrodes, short-circuit or insufficient insulation between magnetic shield layers and element layer, which had been serious problem for narrowing the read gap in the CIP structure never inherently occurs. Therefore, the CPP structure lends itself to a high recording density head.
In the thin-film magnetic head with the CPP structure capable of narrowing the read gap, when it is required to further narrow the read gap in order to scale up high resolution in the track-width direction, the following points are important:    (1) Narrowing a width of a magnetization-free layer or a free layer in a track-width direction of a MR multi-layered structure; and    (2) Narrowing a space between lower and upper magnetic shield layers in the regions outside both side ends in the track-width direction of the MR multi-layered structure.
The easiest way for narrowing the width of the free layer is to use a milling mask with a narrower width in a patterning process for defining the track width of the MR multi-layered structure. However, because there is a physical limitation in narrowing the width of the mask made of a resist material, according to the conventional fabrication method in general, the width of the MR multi-layered structure itself was narrowed as much as possible by performing excess milling. Such excess milling might induce over-etching of not only the MR multi-layered structure itself but also the lower magnetic shield layer in the regions outside both side ends of the MR multi-layered structure. This over-etching of the lower magnetic shield layer causes its side shield effect to reduce and acts counter to the abovementioned point (2). Also, because the point (2) contributes in no small part to increase resolution in the bit direction, the over-etching may deteriorate the bit resolution.